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Tin dioxide
| CASOther = 13472-47-4 (hydrate) | EINECS = 242-159-0 | PubChem = | InChI = | RTECS = XQ4000000 }} | Section2 = | Section3 = | Section4 = | Section7 = | Section8 = }} Tin dioxide is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names (see infobox), this oxide of tin is the most important raw material in tin chemistry. This colourless, diamagnetic solid is amphoteric. Structure It crystallises with the rutile structure, wherein the tin atoms are six coordinate and the oxygen atoms three coordinate. SnO2 is usually regarded as an oxygen-deficient n-type semiconductor.Solid State Chemistry: An Introduction Lesley Smart, Elaine A. Moore (2005) CRC Press ISBN 0-7487-7516-1 Hydrous forms of SnO2 have been described in the past as stannic acids, although such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size. Preparation Tin dioxide occurs naturally but is purified by reduction to the metal followed by burning tin in air. Annual production is in the range of 10 kilotons. SnO2 is reduced industrially to the metal with carbon in a reverbatory furnace at 1200-1300 °C.Tin: Inorganic chemistry,J L Wardell, Encyclopedia of Inorganic Chemistry ed R. Bruce King, John Wiley & Son Ltd., (1995) ISBN 0-471-93620-0 Amphoterism Although SnO2 is insoluble in water, it is an amphoteric oxide, although cassiterite ore has been described as difficult to dissolve in acids and alkalis.Inorganic & Theoretical chemistry, F. Sherwood Taylor, Heineman, 6th Edition (1942) "Stannic acid" refers to hydrated tin dioxide, SnO2, which is also called "stannic hydroxide." Tin oxides dissolve in acids. Halogen acids attack SnO2 to give hexahalostannates,Donaldson & Grimes in Chemistry of tin ed. P.G. Harrison Blackie (1989) such as SnI62-. One report describes reacting a sample in refluxing HI for many hours. :SnO2 + 6 HI → H2SnI6 + 2 H2O Similarly, SnO2 dissolves in sulfuric acid to give the sulfate: :SnO2 + 2 H2SO4 → Sn(SO4)2 + 2 H2O SnO2 dissolves in strong base to give "stannates," with the nominal formula Na2SnO3. Dissolving the solidified SnO2/NaOH melt in water gives Na2Sn(OH)62, "preparing salt," which is used in the dye industry. Uses In conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides. Tin dioxide has long been used as an opacifier and as a white colorant in ceramic glazes.’The Glazer’s Book’ – 2nd edition. A.B.Searle.The Technical Press Limited. London. 1935. Its use has been particular common in glazes for earthenware, sanitaryware and wall tiles; see the articles tin-glazing and Tin-glazed pottery. Tin oxide remains in suspension in vitreous matrix of the fired glazes, and, with its high refractive index being sufficiently different from the matrix, light is scattered, and hence increases the opacity of the glaze. The degree of dissolution increases with the firing temperature, and hence the extent of opacity diminishes.’A Treatise On Ceramic Industries.’ E.Bourry. Fourth edition. Scott, Greenwood & son. London. 1926. Although dependant on the other constituents the solubility of tin oxide in glaze melts is generally low. Its solubility is increased by Na2, K2 and B2O3, and reduced by CaO, BaO, ZnO, Al2O3, and to a limited extent PbO.’Ceramic Glazes’ Third edition. C.W.Parmelee & C.G.Harman. Cahners Books, Boston, Massachusetts. 1973. SnO2 wires are commonly used as the detecting element in carbon monoxide detectors. SnO2 coatings can be applied using chemical vapor deposition, vapour deposition techniques that employ SnCl4 or organotin trihalides e.g. butyltin trichloride as the volatile agent. This technique is used to coat glass bottles with a thin (<0.1 μm) layer of SnO2, which helps to adhere a subsequent, protective polymer coating such as polyethylene to the glass. Thicker layers doped with Sb or F ions are electrically conducting and used in electroluminescent devices. SnO2 has been used as pigment in the manufacture of glasses, enamels and ceramic glazes. Pure SnO2 gives a milky white colour; other colours are achieved when mixed with other metallic oxides e.g. V2O5 yellow; Cr2O3 pink; and Sb2O5 grey blue. SnO2 has been used as a polishing powder and is sometimes known as "putty powder", SnO2 is used in sensors of combustible gases. In these the sensor area is heated to a constant temperature (few hundred °C) and in the presence of a combustible gas the electrical resistivity drops.Joseph Watson The stannic oxide semiconductor gas sensor in The Electrical engineering Handbook 3d Edition; Sensors Nanoscience Biomedical Engineering and Instruments ed R.C Dorf CRC Press Taylor and Francis ISBN 0-8493-7346-8 Doping with various compounds has been investigated (e.g. with CuO http://www.scielo.br/pdf/mr/v9n3/31795.pdf). Doping with cobalt and manganese, gives a material that can be used in e.g. high voltage varistors. Tin dioxide can be doped into the oxides of iron or manganese. References Category:Oxides Category:Tin compounds Category:Semiconductor materials Category:Common oxide glass components cs:Oxid cíničitý de:Zinn(IV)-oxid fr:Dioxyde d'étain ko:산화 주석 it:Diossido di stagno hu:Ón-dioxid nl:Tin(IV)oxide pt:Dióxido de estanho simple:Tin(IV) oxide sv:Tenndioxid vi:Thiếc điôxít zh:二氧化锡